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Astronomy

Orbits of moons, planets, comets and satellites

  • 3 things to know
  • Paper 1

Overview

The shapes of the orbits of planets, the Moon and comets, why a comet moves fastest near the Sun, and the orbits and uses of geostationary and low polar satellites.

What you need to know

Answer each one before you reveal it.

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Key term

Describe the orbit of the Moon around the Earth.

Key term

Explain why a comet travels fastest at the point in its orbit closest to the Sun.

Key term

Describe the orbit of a geostationary satellite.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Describe the shape of the orbit of a planet around the Sun.

    Model answer

    It is a slightly elliptical orbit that is very close to a circle.

  2. 2

    Describe the orbit of the Moon around the Earth.

    Model answer

    The Moon travels in a nearly circular orbit around the Earth, held in place by the Earth's gravity.

  3. 3

    Describe the shape of the orbit of a comet around the Sun.

    Model answer

    A comet follows a very elongated elliptical orbit that brings it close to the Sun and then carries it far beyond the planets.

  4. 4

    Explain why a comet travels fastest at the point in its orbit closest to the Sun.

    Model answer

    The Sun's gravitational pull is strongest there, so the comet accelerates as it approaches and reaches its greatest speed at that point.

  5. 5

    Describe the orbit of a geostationary satellite.

    Model answer

    A geostationary satellite orbits high above the equator once every 24 hours, so it stays above the same point on the Earth's surface.

  6. 6

    Give one use of a geostationary satellite.

    Model answer

    Communications such as television or telephone signals, because a dish on the ground can point at a fixed position in the sky.

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